1. Technical Field
The present invention relates to a liquid-jet head which ejects liquid from nozzle orifices, a method of manufacturing the same, and a liquid-jet apparatus. Particularly, the invention relates to: an ink-jet recording head, in which a part of pressure generating chambers communicating with nozzle orifices ejecting ink droplets is constructed of a vibration plate, piezoelectric elements are formed on a surface of this vibration plate, and displacement of the piezoelectric elements allows ink to be ejected; a method of manufacturing the same; and an ink-jet recording apparatus.
2. Related Art
As an inkjet recording head, in which a part of each of pressure generating chambers communicating with nozzle orifices ejecting ink droplets is constructed of a vibration plate, and this vibration plate is deformed by piezoelectric elements to apply pressure to ink in the pressure generating chambers, and thereby ink droplets are ejected from the nozzle orifices, two types have been put to practical use. One of these two types uses a piezoelectric actuator of a longitudinal vibration mode, which extends and contracts in an axial direction of a piezoelectric element. The other uses a piezoelectric actuator of a flexural vibration mode.
The former type is capable of changing a volume of each pressure generating chamber by having end faces of piezoelectric elements abut a vibration plate, and therefore can be manufactured as a head suitable for high-density printing. On the other hand, this type requires: a difficult process of cutting the piezoelectric elements into a comb-tooth shape while aligning the piezoelectric elements with arrangement pitches of the nozzle orifices; and an operation of positioning and fixing the cut piezoelectric elements with the pressure generating chambers. Accordingly, this type has a problem that a manufacturing process is complicated.
To the contrary, in the latter type, the piezoelectric elements can be built into the vibration plate by a relatively simple process where a green sheet of a piezoelectric material is attached to the vibration plate in accordance with a shape of the pressure generating chamber, and then baked. Nevertheless, a certain area is required for the use of flexure vibration, whereby this type has a problem that high-density arrangement is difficult.
Meanwhile, in order to eliminate the inconvenience of a recording head of the latter type, there has been proposed a recording head in which: a uniform piezoelectric material layer is formed on an entire surface of a vibration plate by use of a deposition technology; and by cutting this piezoelectric material layer into shapes corresponding to pressure generating chambers by use of a lithography method, piezoelectric elements are formed to be independent from one another in a manner respectively corresponding to the pressure generating chambers.
In the piezoelectric elements thus formed, a lower electrode is provided continuously across plural piezoelectric elements, and is set as a common electrode, and upper electrodes are set as individual electrodes of the respective piezoelectric elements. By selectively applying a voltage between this lower electrode and each of the upper electrodes, the desired piezoelectric elements are driven. Each of the piezoelectric elements thus formed assumes a structure where the piezoelectric layer and the upper electrode are provided so as to extend, in a longitudinal direction of that piezoelectric element, from that piezoelectric element to areas outside of regions facing the pressure generating chamber.
However, this recoding head has a problem that an electric discharge occurs between each of the upper electrodes and the lower electrode, and eventually causes dielectric breakdown of the piezoelectric layer, because electric field concentration occurs in end portions of the piezoelectric layers and the upper electrodes in a lead-out side thereof.
For this reason, there has been proposed a structure where narrow-width portions in the lower electrode, which are narrower than the other portions thereof, are formed so that dielectric breakdown of the piezoelectric layers is prevented by these narrow width portions (refer to, for example, JP-A-2000-246892 (pp. 5 to 6, FIGS. 5 to 6)).
In such a configuration where the narrow-width portion is thus formed in the lower electrode, the narrow-width portion has to be formed by patterning when the lower electrode is patterned, whereby pattern formation for this configuration is complicated. In addition, alignment of the narrow-width portion with the piezoelectric layer and the upper electrode is required, whereby, if an arrangement density of the piezoelectric elements becomes high-density, there arises a problem that the alignment is difficult.
Note that, obviously, the aforementioned problems exist not only with an ink-jet recording head, but also with other liquid-jet heads which eject liquid other than ink in like manner.
JP-A-2000-246892 (pp. 5 to 6, FIGS. 5 to 6) is an example of related art.
In consideration of the situation as described above, an object of the present invention is to provide: a liquid-jet head capable of enhancing durability thereof when it is driven, and making an arrangement density of piezoelectric elements high-density; a method of manufacturing the same; and a liquid-jet apparatus.